Entropy of relativistic Boltzmann gas?

[mathlete]

Homework Statement

I'm given a relativistic Boltzmann gas and told to find the entropy

Homework Equations

$$\epsilon = pc$$
p = 3d momentum
c = speed of light

The Attempt at a Solution

I tried to start by finding the partition function, from which I can just take the derivative, but I don't know how I would sum the energies. Would I merely use p=hw/2*pi summed over all frequencies from 0 to infinity?

 

[dextercioby]

The treatment of a photon gas within quantum statistics is a classical subject of statistical physics texts. So open a book...